Donepezil Alzheimer's drug. Computer model of a molecule of the Alzheimer's drug donepezil. Atoms are represented as spheres and are colour-coded: carbon (gold), hydrogen (white), nitrogen (green) and oxygen (purple). Donepezil belongs to a class of drugs known as cholinesterase inhibitors. It inhibits the enzyme acetylcholinesterase, which destroys the neurotransmitter acetylcholine. Lack of neurotransmitters is thought to play a role in Alzheimer's disease, a common cause of dementia in the elderly. Donepezil does not cure the disease, or slow its progression, but it can improve cognitive function.